Bent Pushrod on Startup

[War Wagon]

Started up our rebuilt engine today and right off there was a pop and then valve train noise from the drivers side valve cover. As we ran the engine to break it in the noise got worse so we shut it down and pulled the valve cover. We found a bent pushrod on #7 cylinder, replaced it with one of the used ones we had and all is well. We finished breaking in the engine at 2500 RPM's for 15 minutes and changed the oil. Cranked it back up and all is well, no noise at all. Now did the small backfire bend the pushrod?

The Cam specs are 212/218 duration @ 0.050" lift.
.477/.484 lift on a 110 LS
We set it a 4 degrees advanced
Springs are CC 926-16

Jim

[82Waggy]

Probably a stuck valve. Either the guide was dirty, not lubed properly at assembly, or too tight.

Be careful. May have damaged the cam lobe or lifter as well.

[ironman_gq]

had similar problems after my timing chain skipped. didn't bend any then but when I started her up after replacing the chain she made some god awfull noises. I later found out that I broke one rod and bent 3 others. one was shaped like a ? suprisingly no bent valves. :shock:

[fifesjeep]

Could be a wide range of possibilities... Like what was already mentioned... Maybe a lifter spring broke etc... But, if you ran it after you heard a noise and then it got worse chances are you might have done more damage! I'd definitely inspect the cam and lifter...

[War Wagon]

The noise started out like a ticking at the rocker arms, the engine made more noise before the rebuild. On the second break in run it got louder so we shut it down and found the problem. After replacing the pushrod there is no noise at all and she runs great. This thing fires up at the first hit of the key and idles at 600 RPM with no problems. I recurved the distributor and am running 22 degrees mechanical advance in by 2500 with the light springs. I have the base timing set to 15 degrees BTDC. Man this thing has great throttle responce. A/F ratio is running at 13.5 to 1 at WOT for now, need to free up the exhaust some.

Jim

[ironman_gq]

13.5 at WOT is pretty good. A little rich won't hurt you much and will keep the engine from burning down.